The purpose of this project is to analyze the cellular control of immune function in normal individuals and in certain patients with neoplastic disease. We are currently determining the helper and suppressor activity of neoplastic T cells from patients with acute lymphoblastic leukemia and cutaneous T-cell lymphomas and also the capacity to induce differentiation in these cells. We are also studying abnormalities of regulatory monocytes and T-cells from patients with multiple myeloma and mice bearing plasmacytomas. We are characterizing the capacity of antibodies directed against surface membrane products of immune response genes to inhibit human immune reactions by activating regulatory T cells. We have analyzed the expression of T-cell Fc receptors and the role of cytoskeletal structures in normal Fc expression.